In a subnetwork of a shared network, for example, the Ethernet, PIM equipment (which may also be called a PIM router) may elect a DR based on a PIM protocol. Specifically, the PIM equipment may determine itself as a DR by default after an interface is UP (a state specified in the protocol), and may perform DR reelection to select a new DR after receiving a Hello message (a message specified in the protocol). A message sent when an Internet Group Management Protocol (IGMP) or Multicast Listener Discover (MLD) user joins or leaves a group may be received by all equipment in the network, and a DR is responsible for forwarding multicast traffic to users in the subnetwork.
When an elected DR in a subnetwork fails, another DR in the subnetwork may need to be elected to forward traffic to a network. This process may generate the following delays: a time T1 for detecting a failure of the DR; a time T2 for sending PIM joining to an upstream Rendezvous Point (RP) or DR equipment directly connected to the source; and a time T3 for pushing traffic to new DR equipment. When not considering the condition of time for transferring equipment routing to a forwarding plane, packets of a user may be lost within a delay of T1+T2+T3. In a complex networking or capacity environment, this delay becomes more detectable.